Even though incidencia/incidente may be considered synonyms [DRAE: "Acontecimiento que sobreviene en el curso de un asunto o negocio y tiene con él alguna conexión"], gestión de incidencias, in an emergency context, conveys management of discrete everyday problems while gestión de incidentes conveys management of major situations or those with far-reaching implications.
CDC translation of IMS as sistema de gestión de incidencias in the context of an EOC [
https://www.cdc.gov/cdctv/spanish/emergencypreparednessandre... ] could well be considered a mistake and an example of the occasional difficulty of translating contex-dependant "incident" -which by the way may point to the relevance of those sometimes taken-for-granted basic translations in specialized glossaries.
And yes, I get the irony of this all...